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Context. It has been shown that convection in red supergiant stars gives rise to large granules causing surface inhomogeneities together with shock waves in the photosphere. The resulting motion of the photocenter (on time scales ranging…

Solar and Stellar Astrophysics · Physics 2015-05-20 A. Chiavassa , E. Pasquato , A. Jorissen , S. Sacuto , C. Babusiaux , B. Freytag , H. -G. Ludwig , P. Cruzalebes , Y. Rabbia , A. Spang , O. Chesneau

Local-box hydrodynamical model atmospheres provide statistical information about the spatial dependence, as well as temporal evolution, of a star's emergent radiation field. Here, we consider late-type stellar atmospheres for which temporal…

Astrophysics · Physics 2009-11-11 Hans-G. Ludwig

Convection plays an essential role in the emerging intensity for many stars that will be observed by Gaia. Convective-related surface structures affect the shape, shift, and asymmetry of absorption lines, the phocentric and photometric…

Solar and Stellar Astrophysics · Physics 2011-12-13 A. Chiavassa , L. Bigot , F. Thevenin , R. Collet , G. Jasniewicz , Z. Magic , M. Asplund

Local-box hydrodynamical model atmospheres provide statistical information about a star's emergent radiation field which allows one to predict the level of its granulation-related micro-variability. Space-based photometry is now…

Solar and Stellar Astrophysics · Physics 2015-05-13 H. -G. Ludwig , R. Samadi , M. Steffen , T. Appourchaux , F. Baudin , K. Belkacem , P. Boumier , M. -J. Goupil , E. Michel

Radiation-hydrodynamical simulations of surface convection in low-mass stars can be exploited to derive estimates of i) the efficiency of the convective energy transport in the stellar surface layers; ii) the convection-related photometric…

Astrophysics · Physics 2009-11-13 Hans-G. Ludwig , Elisabetta Caffau , Arunas Kucinskas

During the recent years significant progress has been made in the modeling of red giant atmospheres with the aid of 3D hydrodynamical model atmosphere codes. In this contribution we provide an overview of selected results obtained in this…

Solar and Stellar Astrophysics · Physics 2013-05-16 A. Kucinskas , H. -G. Ludwig , M. Steffen , V. Dobrovolskas , J. Klevas , D. Prakapavicius , E. Caffau , P. Bonifacio

Context. Asymptotic Giant Branch stars are characterised by complex stellar surface dynamics that affect the measurements and amplify the uncertainties on stellar parameters. The resulting motion of the stellar photo-center could have…

Solar and Stellar Astrophysics · Physics 2018-09-12 A. Chiavassa , B. Freytag , M. Schultheis

Our ability to predict the structure and evolution of stars is in part limited by complex, 3D hydrodynamic processes such as convective boundary mixing. Hydrodynamic simulations help us understand the dynamics of stellar convection and…

We studied the influence of convection on the spectral energy distributions, photometric magnitudes, and colour indices of different types of stars across the H-R diagram. The 3D hydrodynamical CO5BOLD, averaged <3D>, and 1D hydrostatic LHD…

Solar and Stellar Astrophysics · Physics 2018-05-30 A. Kučinskas , J. Klevas , H. -G. Ludwig , P. Bonifacio , M. Steffen , E. Caffau

Red supergiants are massive evolved stars that contribute extensively to the chemical enrichment of our Galaxy. It has been shown that convection in those stars gives rise to large granules that cause surface inhomogeneities and shock waves…

Solar and Stellar Astrophysics · Physics 2015-05-30 A. Chiavassa , B. Freytag , T. Masseron , B. Plez

Radiative hydrodynamic simulations of solar and stellar surface convection have become an important tool for exploring the structure and gas dynamics in the envelopes and atmospheres of late-type stars and for improving our understanding of…

Solar and Stellar Astrophysics · Physics 2015-06-03 B. Beeck , R. Collet , M. Steffen , M. Asplund , R. H. Cameron , B. Freytag , W. Hayek , H. -G. Ludwig , M. Schüssler

Red supergiant (RSGs) are cool massive stars in a late phase of their evolution when the stellar envelope becomes fully convective. They are the brightest stars in the universe at infrared light and can be detected in galaxies far beyond…

Solar and Stellar Astrophysics · Physics 2022-05-12 A. Chiavassa , R. Kudritzki , B. Davies , B. Freytag , S. E. de Mink

Hydrodynamical, i.e. multi-dimensional and time-dependent, model atmospheres of late-type stars have reached a high level of realism. They are commonly applied in high-fidelity work on stellar abundances but also allow the study of…

Solar and Stellar Astrophysics · Physics 2016-10-19 Hans-G. Ludwig , Matthias Steffen

Context. The complex dynamics of asymptotic giant branch (AGB) stars and the resulting stellar winds have a significant impact on the measurements of stellar parameters and amplify their uncertainties. Three-dimensional (3D) radiative…

Solar and Stellar Astrophysics · Physics 2024-09-06 E. Béguin , A. Chiavassa , A. Ahmad , B. Freytag , S. Uttenthaler

Advances in hydrodynamical simulations have provided new insights into the effects of convection on the frequencies of solar oscillations. As more accurate observations become available, this may lead to an improved understanding of the…

The Microvariability and Oscillations of STars (MOST) photometric satellite has already undertaken more than 64 primary campaigns which include some clusters and has obtained observations of >850 secondary stars of which ~180 are variable.…

Astrophysics · Physics 2009-06-23 Gordon A. H. Walker

Context. The surface structures and dynamics of cool stars are characterized by the presence of convective motions and turbulent flows which shape the emergent spectrum. Aims. We used realistic three-dimensional radiative hydrodynamical…

Solar and Stellar Astrophysics · Physics 2018-03-14 A. Chiavassa , L. Casagrande , R. Collet , Z. Magic , L. Bigot , F. Thevenin , M. Asplund

Recent photometric observations of massive stars have identified a low-frequency power excess which appears as stochastic low-frequency variability in light curve observations. We present the oscillation properties of high resolution…

Solar and Stellar Astrophysics · Physics 2024-05-01 William Thompson , Falk Herwig , Paul R. Woodward , Huaqing Mao , Pavel Denissenkov , Dominic M. Bowman , Simon Blouin

Broadening and asymmetry of spectral lines in slowly rotating late A-type stars provide evidence for high-amplitude convective motions. The properties of turbulence observed in the A-star atmospheres are not understood theoretically and…

Astrophysics · Physics 2015-06-24 O. Kochukhov , B. Freytag , N. Piskunov , M. Steffen

Large scale surface convection on red supergiants (RSGs) can lead to shifts in the photocenter of the star which might be measured by Gaia and used as a new probe of the surface dynamics of these rare but important stars. Unlike brightness…

Solar and Stellar Astrophysics · Physics 2022-10-05 C. S. Kochanek
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